U.S. patent application number 13/652861 was filed with the patent office on 2013-05-09 for liquid crystal display device.
The applicant listed for this patent is Tatsuaki KUJI, Arihiro TAKEDA. Invention is credited to Tatsuaki KUJI, Arihiro TAKEDA.
Application Number | 20130114033 13/652861 |
Document ID | / |
Family ID | 48223467 |
Filed Date | 2013-05-09 |
United States Patent
Application |
20130114033 |
Kind Code |
A1 |
KUJI; Tatsuaki ; et
al. |
May 9, 2013 |
LIQUID CRYSTAL DISPLAY DEVICE
Abstract
In one embodiment, a liquid crystal display device includes a
first substrate and a second substrate arranged facing the first
substrate with a gap. A plurality of pixels is arranged in a matrix
of a first direction and a second direction orthogonally crossing
the first direction. The length of the pixel along the first
direction is shorter than that along the second direction. Each
pixel includes a main pixel electrode formed on the first substrate
extending in the second direction, and main common electrodes
formed on the second substrate extending in the second direction
and arranged so as to sandwich the main pixel electrode in the
first direction. Further, each pixel includes a plurality of
regions in which an inter-electrode distance between the main pixel
electrode and the main common electrode in the first direction
differs mutually in the respective regions.
Inventors: |
KUJI; Tatsuaki;
(Saitama-ken, JP) ; TAKEDA; Arihiro; (Saitama-ken,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KUJI; Tatsuaki
TAKEDA; Arihiro |
Saitama-ken
Saitama-ken |
|
JP
JP |
|
|
Family ID: |
48223467 |
Appl. No.: |
13/652861 |
Filed: |
October 16, 2012 |
Current U.S.
Class: |
349/143 |
Current CPC
Class: |
G02F 2001/134381
20130101; G02F 1/134336 20130101; G02F 1/134309 20130101; G02F
1/134363 20130101 |
Class at
Publication: |
349/143 |
International
Class: |
G02F 1/1343 20060101
G02F001/1343 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 8, 2011 |
JP |
2011-244529 |
Claims
1. A liquid crystal display device, comprising: a first substrate;
a second substrate arranged facing the first substrate with a gap;
a plurality of pixels arranged in a matrix of a first direction and
a second direction orthogonally crossing the first direction, the
length of the pixel along the first direction being shorter than
that along the second direction, and each pixel including; a main
pixel electrode formed on the first substrate extending in the
second direction, and main common electrodes formed on the second
substrate extending in the second direction and arranged so as to
sandwich the main pixel electrode in the first direction, wherein
each pixel includes a plurality of regions in which an
inter-electrode distance between the main pixel electrode and the
main common electrode in the first direction differs mutually in
the respective regions.
2. The liquid crystal display device according to claim 1, wherein
at least one of the widths of the main pixel electrode and the main
common electrode is different in every region of each pixel
3. The liquid crystal display device according to claim 1, wherein
the pixel further includes a wiring layer formed on the first
substrate or the second substrate and extending in the first
direction, and the plurality of regions of each pixel is separated
by the wiring layer.
4. The liquid crystal display device according to claim 1, wherein
the plurality of regions of each pixel is adjacent in the second
direction.
5. The liquid crystal display device according to claim 1, wherein
the plurality of regions of each pixel is adjacent in the first
direction.
6. A liquid crystal display device, comprising: a first substrate;
a second substrate arranged facing the first substrate with a gap;
a plurality of pixels arranged in a matrix of a first direction and
a second direction orthogonally crossing the first direction, the
length of the pixel along the first direction being shorter than
that along the second direction, and each pixel including; a main
pixel electrode formed on the first substrate extending in the
second direction, and main common electrodes formed on the second
substrate extending in the second direction and arranged so as to
sandwich the main pixel electrode in the first direction, wherein
each pixel includes a first region and a second region separated by
a wiring layer crossing the center of the pixel in which
inter-electrode distance between the main pixel electrode and the
main common electrode in the first direction differs mutually in
the first and second regions, and the first and second regions are
arranged adjacent in the second direction.
7. The liquid crystal display device according to claim 6, wherein
at least one of the widths of the main pixel electrode and the main
common electrode is different in the first and second regions in
each pixel.
8. A liquid crystal display device, comprising: a first substrate;
a second substrate arranged facing the first substrate with a gap;
and a plurality of pixels arranged in a matrix of a first direction
and a second direction crossing the first direction, the length of
the pixel along the first direction being shorter than that along
the second direction, and each pixel including first and second
main common electrodes formed on the second substrate extending in
the second direction, wherein the pixel includes a first region and
a second region separated by a wiring layer crossing the center of
the pixel, the first region includes a first main pixel electrode
formed on the first substrate sandwiched by the first and second
main common electrodes and extending in the second direction
substantially in the center portion of the pixel, the second region
includes second and third main pixel electrodes formed on the first
substrate and connected with the first main pixel electrode
extending in the second direction, and a third main common
electrode formed on the second substrate and connected with the
first and second main common electrodes extending in the second
direction substantially in the center portion of the pixel, the
second main pixel electrode is arranged substantially in the center
between the first main common electrode and the third main common
electrode, and the third main pixel electrode is arranged
substantially in the center between the third main common electrode
and the second main common electrode, and a first inter-electrode
distance between the first main common electrode and the first main
pixel electrode in the first region is larger than a second
inter-electrode distance between the first main common electrode
and the second main pixel electrode in the second region.
9. The liquid crystal display device according to claim 8, wherein
the first and second regions of each pixel are adjacent in the
second direction.
10. The liquid crystal display device according to claim 8, wherein
the wiring layer is formed of an auxiliary capacitance line formed
on the first substrate.
11. The liquid crystal display device according to claim 10,
wherein a sub-pixel electrode is arranged overlapping with the
auxiliary capacitance line on the first substrate.
12. The liquid crystal display device according to claim 11,
wherein the first main pixel electrode is connected with the second
and third main pixel electrodes through the sub-pixel electrode.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is based upon and claims the benefit of
priority from prior Japanese Patent Application No. 2011-244529,
filed Nov. 8, 2011, the entire contents of which are incorporated
herein by reference.
FIELD
[0002] Embodiments described herein relate generally to a liquid
crystal display device.
BACKGROUND
[0003] In recent years, a flat panel display is developed briskly.
Especially, the liquid crystal display device gets a lot of
attention from advantages, such as light weight, thin shape, and
low power consumption. In an active matrix type liquid crystal
display device equipped with a switching element in each pixel, a
structure using lateral electric field, such as IPS (In-Plane
Switching) mode and FFS (Fringe Field Switching) mode, attracts
attention. The liquid crystal display device using the lateral
electric field mode is equipped with pixel electrodes and a common
electrode formed in an array substrate, respectively. Liquid
crystal molecules are switched by the lateral electric field
substantially in parallel with the principal surface of the array
substrate.
[0004] On the other hand, another technique is also proposed, in
which the liquid crystal molecules are switched using the lateral
electric field or an oblique electric field between the pixel
electrode formed in the array substrate and the common electrode
formed in a counter substrate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] The accompanying drawings, which are incorporated in and
constitute a part of the specification, illustrate embodiments of
the invention, and together with the general description given
above and the detailed description of the embodiments given below,
serve to explain the principles of the invention.
[0006] FIG. 1 is a figure schematically showing a structure and the
equivalent circuit of a liquid crystal display device according to
one embodiment.
[0007] FIG. 2A is a plan view schematically showing a structure of
one pixel when the liquid crystal display panel shown in FIG. 1 is
seen from a counter substrate side.
[0008] FIGS. 2B and 2C are figures showing the relation between
polarizing plates and an initial alignment direction.
[0009] FIG. 3 is a cross-sectional view schematically showing the
structure taken along line III-III in the liquid crystal display
panel shown in FIG. 2A.
[0010] FIG. 4 is a figure showing an electric field formed between
a pixel electrode and a common electrode and a relation between a
director and a transmissivity of the liquid crystal molecule by
this electric field in the liquid crystal display panel shown in
FIG. 2A.
[0011] FIG. 5 is a plan view schematically showing a structure of
one pixel when the liquid crystal display panel of a comparative
example of the embodiment is seen from the counter substrate
side
[0012] FIG. 6 is a figure showing change of transmissivity with
respect to voltage in the liquid crystal display device according
to the embodiment and the comparative example in a graph.
[0013] FIG. 7 is a figure showing change of relative brightness
with respect to gradient at the time of white display of the liquid
crystal display device according to the embodiment and the
comparative example in a graph.
[0014] FIG. 8 is a plan view schematically showing a structure of
one pixel when the liquid crystal display panel is seen from the
counter substrate side according to a second embodiment.
[0015] FIG. 9 is a plan view schematically showing a structure of
one pixel when the liquid crystal display panel of the comparative
example of the second embodiment shown in FIG. 8 is seen from the
counter substrate side.
DETAILED DESCRIPTION
[0016] A liquid crystal display device according to an exemplary
embodiment of the present invention will now be described with
reference to the accompanying drawings wherein the same or like
reference numerals designate the same or corresponding portion s
throughout the several views.
[0017] According to one embodiment, a liquid crystal display device
includes: a first substrate; a second substrate arranged facing the
first substrate with a gap; a plurality of pixels arranged in a
matrix of a first direction and a second direction orthogonally
crossing the first direction, the length of the pixel along the
first direction being shorter than that along the second direction,
and each pixel including; a main pixel electrode formed on the
first substrate extending in the second direction, and main common
electrodes formed on the second substrate extending in the second
direction and arranged so as to sandwich the main pixel electrode
in the first direction, wherein each pixel includes a plurality of
regions in which an inter-electrode distance between the main pixel
electrode and the main common electrode in the first direction
differs mutually in the respective regions.
[0018] FIG. 1 is a figure schematically showing a structure and the
equivalent circuit of a liquid crystal display device according to
one embodiment.
[0019] The liquid crystal display device includes an active-matrix
type liquid crystal display panel LPN. The liquid crystal display
panel LPN is equipped with an array substrate AR as a first
substrate, a counter substrates CT as a second substrate arranged
opposing the array substrate AR, and a liquid crystal layer LQ held
between the array substrate AR and the counter substrate CT. The
liquid crystal display panel LPN includes a display area R1 which
displays images. The display area R1 overlaps with the array
substrate AR, the counter substrate CT and the liquid crystal layer
LQ. The display area R1 is constituted by a plurality of pixels PX
arranged in the shape of a (m.times.n) matrix (here, "m" and "n"
are positive integers).
[0020] The liquid crystal display panel LPN is equipped with "n"
gate lines G (G1-Gn), "n" auxiliary capacitance lines C (C1-Cn),
"m" source lines S (S1-Sm), etc., in the display area R1. The gate
line G and the auxiliary capacitance line C linearly extend in a
first direction X, for example. The gate line G and the auxiliary
capacitance line C are arranged in turns along a second direction Y
that orthogonally intersects the first direction X. The source
lines S cross the gate lines G and the auxiliary capacitance lines
C. The source lines S linearly extend in the second direction Y.
The gate line G, the auxiliary capacitance line C and the source
line S do not necessarily extend linearly, and a portion thereof
may be crooked partially.
[0021] Each gate line G is pulled out to outside of the display
area R1, and is connected to a gate driver GD. Each source line S
is pulled out to the outside of the display area R1, and is
connected to a source driver SD. At least a portion of the gate
driver GD and the source driver SD is formed in the array substrate
AR, for example, and is connected with the driver IC chip 2
provided in the array substrate AR and having an implemented
controller.
[0022] Each pixel PX includes a switching element SW, a pixel
electrode PE, a common electrode CE, etc. Retention capacitance Cs
is formed, for example, between the auxiliary capacitance line C
and the pixel electrode PE. The auxiliary capacitance line C is
electrically connected with a voltage impressing portion VCS to
which an auxiliary capacitance voltage is impressed.
[0023] In addition, in the liquid crystal display panel LPN
according to this embodiment, while the pixel electrode PE is
formed in the array substrate AR, at least one portion of the
common electrode CE is formed in the counter substrate CT. Liquid
crystal molecules of the liquid crystal layer LQ are switched
mainly using an electric field formed between the pixel electrode
PE and the common electrode CE. The electric field formed between
the pixel electrode PE and the common electrode CE is an oblique
electric field slightly oblique with respect to an X-Y pane
specified by the first direction and the second direction, i.e.,
the substrates (or lateral electric field substantially in parallel
with the principal surface of the substrate).
[0024] The switching element SW is constituted by an n channel type
thin film transistor (TFT), for example. The switching element SW
is electrically connected with the gate line G and the source line
S. The switching element SW may be either a top-gate type or a
bottom-gate type. Though the semiconductor layer is formed of
poly-silicon, the semiconductor layer may be formed of amorphous
silicon.
[0025] The pixel electrode PE is arranged in each pixel PX and
electrically connected with the switching element SW. The common
electrode CE is arranged in common to the plurality of pixel
electrodes PE of the pixels PX through the liquid crystal layer LQ.
Though the pixel electrode PE and the common electrode CE are
formed by light transmissive conductive materials, such as Indium
Tin Oxide (ITO), Indium Zinc Oxide (IZO), etc., other metals such
as aluminum may be used.
[0026] The array substrate AR includes an electric power supply
portion VS for impressing a common voltage to the common electrode
CE. The electric power supply portion VS is, for example, formed in
a non-display area R2 outside of the display area R1. Furthermore,
the common electrode CE is drawn to outside of the active area R1
and electrically connected with an electric power supply portion VS
through an electric conductive component which is not
illustrated.
[0027] FIG. 2A is a plan view schematically showing the structure
of one pixel when the liquid crystal display panel according to a
first embodiment is seen from the counter substrate side. Herein, a
plan view in the X-Y plane is shown.
[0028] In FIG. 2A, the pixel PX has the shape of a rectangle whose
length in the first direction X is shorter than the length in the
second direction Y, as shown in a dashed line. The gate line G1 and
the line G2 extend in the first direction X, respectively. The
auxiliary capacitance line Cl is arranged between the adjacent gate
line G1 and gate line G2 and extends in the first direction X. The
source line S1 and the source line S2 extend along the second
direction Y, respectively. The pixel electrode PE is located
between the adjacent source line S1 and source line S2. The pixel
electrode PE is also located between the gate line G1 and the gate
line G2.
[0029] In the illustrated example, the source line S1 is arranged
at the left-hand side end in the pixel PX. Precisely, the source
line S1 is arranged striding over a boundary between the
illustrated pixel and a pixel PX adjoining the illustrated pixel PX
on the left-hand side. The source line S2 is arranged at the
right-hand side end. Precisely, the source line S2 is arranged
striding over a boundary between the illustrated pixel and a pixel
PX adjoining the illustrated pixel PX on the right-hand side.
Moreover, in the pixel PX, the gate line G1 is arranged at an upper
end portion. Precisely, the gate line G1 is arranged striding over
a boundary between the illustrated pixel and a pixel which adjoins
the illustrated pixel PX on its upper end side. The gate line G2 is
arranged at a lower end portion. Precisely, the gate line G2 is
arranged striding over a boundary between the illustrated pixel and
a pixel adjoining the illustrated pixel PX on its lower end side.
The auxiliary capacitance line C1 is arranged substantially in the
center of the pixel.
[0030] The switching element SW is electrically connected with the
gate line G1 and the source line S1 in the illustrated example.
Namely, the switching element SW is formed in an intersection of
the gate line G1 and the source line S1. A drain line extending
along the source line S1 and the auxiliary capacitance line C1 is
electrically connected with the pixel electrode PE in a region
which overlaps with the auxiliary capacitance line C1 through a
contact hole CH. The switching element SW is formed in the
overlapped region with the source line S1 and the auxiliary
capacitance line C1, and hardly runs off the overlapped region.
Thereby, reduction of the area of an aperture portion which
contributes to the display is suppressed when the switching element
SW is arranged in the pixel PX.
[0031] A plurality of pixel electrodes PE is arranged with a gap
therebetween in the first direction X and the second direction Y.
The plurality of pixel electrodes PE includes one or more main
pixel electrodes PA formed extending along the second direction Y,
respectively.
[0032] In this embodiment, the pixel electrode PE includes a main
pixel electrode PA, a sub-pixel electrode PF, and a sub-pixel
electrode PG electrically connected mutually. Hereinafter, in order
to distinguish the main pixel electrode PA, the main pixel
electrode of the upper portion in the figure is called PAU, and the
main pixel electrode of the lower portion in the figure is called
PAB.
[0033] The main pixel electrode PAB linearly extends along the
second direction Y from the sub-pixel electrode PF to a vicinity of
a lower end of the pixel PX. The main pixel electrode PAB is formed
in the shape of a belt having substantially the same width along
the first direction X. The main pixel electrode PAU linearly
extends along the second direction Y from the sub-pixel electrode
PF to a vicinity of an upper end of the pixel PX. The main pixel
electrode PAU is formed in the shape of a belt having substantially
the same width along the first direction X.
[0034] The sub-pixel electrode PF extends along the first direction
X. The sub-pixel electrode PF is located in a region which overlaps
with the auxiliary capacity line C1, and is electrically connected
with the switching element SW through the contact hole CH.
[0035] The sub-pixel electrode PG extends along the first direction
X. The sub-pixel electrode PG is located near the upper end of the
pixel PX. The sub-pixel electrode PG is electrically connected with
the main pixel electrode PAU.
[0036] The sub-pixel electrodes PF and PG are formed more broadly
than the main pixel electrodes PAB and PAU. The pixel electrode PE
is arranged in the center of the pixel PX. The inter-electrode
distance between the source line S1 and the main pixel electrode
PAB in the first direction X is substantially the same as that
between the source line S2 and the main pixel electrode PAB in the
first direction X. The inter-electrode distance between the source
line S1 and the main pixel electrode PAU in the first direction X
is substantially the same as that between the source line S2 and
the main pixel electrode PAU in the first direction X.
[0037] The common electrodes CE includes a pair of common
electrodes CA arranged on both sides of the main pixel electrode
PAB and PAU and extending along the second direction Y. In this
embodiment, the common electrode CE includes the pair of main
common electrodes CA and a sub-common electrode CB.
[0038] The main common electrodes CA are formed on the counter
substrate CT side. The main common electrodes CA are arranged in
the first direction X apart from each other in the X-Y plane
sandwiching the main pixel electrodes PAB and PAU in the first
direction X, respectively, and linearly extend along the second
direction Y substantially in parallel with the main pixel
electrodes PAB and PAU. The main common electrodes CA counter with
the source line S, respectively. The main common electrode CA is
formed in the shape of a belt having substantially the same width
along the first direction X.
[0039] In the illustrated example, the pair of main common
electrodes CA is arranged in two lines along the first direction X,
and is arranged at the right-and-left both ends of the pixel PX,
respectively. Hereafter, in order to distinguish the main common
electrodes CA, the main common electrode of the left-hand side in
the figure is called CAL, and the main common electrode of the
right-hand side in the figure is called CAR. The main common
electrode CAL counters with the source line S1, and the main common
electrode CAR counters with the source line S2.
[0040] In the pixel PX, the main common electrode CAL is arranged
at the left-hand side end, and the main common electrode CAR is
arranged at the right-hand side end. Precisely, the main common
electrode CAL is arranged striding over a boundary between the
illustrated pixel PX and the adjoining pixel PX on its left-hand
side, and the main common electrode CAR is arranged striding over a
boundary between the illustrated pixel PX and the adjoining pixel
PX on its right-hand side.
[0041] If its attention is paid to the positional relationship
between the pixel electrode PE and the main common electrode CA,
the pixel electrode PE and the main common electrode CA are
arranged by turns along the first direction X. The pixel electrodes
PE (the main pixel electrode PA) and the main common electrode CA
are arranged substantially in parallel. At this time, neither of
the main common electrodes CA overlaps with the pixel electrode PE
in the X-Y plane.
[0042] One pixel electrode PE is arranged between the adjoining
main common electrode CAL and main common electrode CAR. That is,
the pair of main common electrodes (the main common electrode CAL
and the main common electrode CAR) is arranged on the both sides
which face across a position right above the pixel electrode PE.
The pixel electrode PE is arranged between the main common
electrode CAL and the main common electrode CAR. For this reason,
the main common electrode CAL, the pixel electrode PE (the main
pixel electrode PA), and the main common electrode CAR are arranged
along the first direction X in this order.
[0043] A sub-common electrode CB is arranged in the center of the
pixel PX extending in the first direction X. The sub-common
electrode CB is arranged so as to counter with the auxiliary
capacity line C. According to this embodiment, the sub-common
electrode CB is formed on the counter substrate CT side, and is
formed integrally or continuously with the main common electrodes
CA.
[0044] For this reason, the sub-common electrode CB is electrically
connected with the main common electrodes CA. The voltage (common
voltage) supplied from the electric power supply portion VS is
supplied to the main common electrodes CA and the sub-common
electrode CB.
[0045] Each pixel PX includes two regions R3 and R4 in which the
inter-electrode distance between the main pixel electrode PA and
the main common electrode CA in the first direction X differs
mutually in the regions R3 and R4. In this embodiment, the width of
the main pixel electrode PAB in the region R3 differs from that of
the main pixel electrode PAU in the region R4 in each pixel PX. The
width of the main pixel electrode PAB arranged in the region R3 is
larger than that of the main pixel electrode PAU arranged in the
region R4. An inter-electrode distance Ga between the main pixel
electrode PAB and the main common electrode CA is smaller than an
inter-electrode distance Gb between the main pixel electrode PAU
and the main common electrode CA.
[0046] The regions R3 and R4 of each pixel PX are separated by a
region on a wiring layer formed on the array substrate AR or the
counter substrate CT extending along the first direction X. In this
embodiment, the above-mentioned wiring layer is the auxiliary
capacity line C1 and the sub-common electrode CB. The regions R3
and R4 in each pixel PX are adjacent in the second direction Y,
each other.
[0047] FIG. 3 is a cross-sectional view schematically showing a
structure taken along line III-III in the liquid crystal display
panel LPN shown in FIG. 2A. In addition, only a portion required
for explanation is illustrated here. The backlight unit 4 is
arranged on the back side of the array substrate AR as shown in
FIG. 3. Various types of backlight unit 4 can be used. For example,
a light emitting diode (LED) or a cold cathode fluorescent lamp
(CCFL), etc., can be applied as a light source of the backlight
unit 4, and the explanation about its detailed structure is
omitted.
[0048] The array substrate AR is formed using a first insulating
substrate 10 which has a transmissive characteristics. The source
line S is formed on a first interlayer insulating film 11, and is
covered with a second interlayer insulating film 12. In addition,
the gate line and the auxiliary capacitance line which are not
illustrated are arranged between the first insulating substrate 10
and the first interlayer insulating film 11, for example. The pixel
electrode PE is formed on the second interlayer insulating film 12.
The pixel electrode PE is located inside of the pixel rather than
the positions on the respective adjoining source lines S.
[0049] A first alignment film AL1 is arranged on the array
substrate AR facing the counter substrate CT, and extends to whole
active area R1. The first alignment film AL1 covers the pixel
electrode PE, etc., and is arranged also on the second interlayer
insulating film 12. The first alignment film AL1 is formed of the
material which shows a horizontal alignment characteristics. In
addition, the array substrate AR may be further equipped with a
portion of the common electrodes CE.
[0050] The counter substrate CT is formed using a second insulating
substrate 20 which has a transmissive characteristics. The counter
substrate CT includes a black matrix BM, a color filter CF, an
overcoat layer OC, the common electrode CE, and a second alignment
film AL2, etc.
[0051] The black matrix BM defines each pixel PX, and forms an
aperture portion AP facing the pixel electrode PE. That is, the
black matrix BM is arranged so that wiring portions, such as the
source line, the gate line, the auxiliary capacitance line, and the
switching element, may counter with the black matrix BM. Herein,
though only a portion of the black matrix BM extending along the
second direction Y is shown, the black matrix BM may include a
portion extending along the first direction X. The black matrix BM
is formed on an internal surface 20A of the second insulating
substrate 20 facing the array substrate AR.
[0052] A color filter CF is arranged corresponding to each pixel
PX. That is, while the color filter CF is arranged in the aperture
portion AP in the internal surface 20A of the second insulating
substrate 20, a portion thereof runs on the black matrix BM. The
colors of the color filters CF arranged in the adjoining pixels PX
in the first direction X differ mutually. For example, the color
filters CF are formed of resin materials colored by three primary
colors of red, blue, and green, respectively. The red color filter
CFR formed of resin material colored in red is arranged
corresponding to the red pixel. The blue color filter CFB formed of
resin material colored in blue is arranged corresponding to the
blue pixel. The green color filter CFG formed of resin material
colored in green is arranged corresponding to the green pixel. The
boundary between the adjoining color filters CF is located in a
position which overlaps with the black matrix BM.
[0053] The overcoat layer OC covers the color filter CF. The
overcoat layer OC eases influence of concave-convex of the surface
of the color filter CF.
[0054] The common electrode CE is formed on the overcoat layer OC
facing the array substrate AR. The distance between the common
electrode CE and the pixel electrode PE along a third direction Z
is substantially the same. Here, the third direction Z is a
direction which intersects perpendicularly the first direction X
and the second direction Y, or a normal line direction of the
liquid crystal panel LPN.
[0055] The second alignment film AL2 is arranged on the counter
substrate CT facing the array substrate AR, and extends to whole
display area R1. The second alignment film AL2 covers the common
electrode CE, the overcoat layer OC, etc. The second alignment film
AL2 is formed of a material showing horizontal alignment
characteristics.
[0056] An alignment treatment (for example, rubbing processing or
light alignment processing) is performed to the first alignment
film AL1 and the second alignment film AL2 to initially align the
molecules of the liquid crystal layer LQ. A first alignment
treatment direction PD1 in which the first alignment film AL1
initially aligns the molecules of the liquid crystal layer LQ and a
second alignment treatment direction PD2 in which the second
alignment film AL2 initially aligns the molecules of the liquid
crystal layer LQ are in parallel, and the same direction or
opposite direction each other. For example, the first alignment
treatment direction PD 1 and the second alignment treatment
direction PD2 are in parallel with the second direction Y and are
opposite directions each other.
[0057] In this embodiment, the first alignment film AL1 and the
second alignment film AL2 can initially align the liquid crystal
molecules near the first and second alignment films AL1 and AL2 in
the second direction Y.
[0058] The array substrate AR and the counter substrate CT as
mentioned-above are arranged so that the first alignment film AL1
and the second alignment film AL2 face each other. In this case, a
pillar-shaped spacer is formed integrally with one of the
substrates by resin material between the first alignment film AL1
on the array substrate AR and the second alignment film AL2 on the
counter substrate CT. Thereby, a predetermined gap, for example, a
2-7 .mu.m cell gap, is formed, for example. The array substrate AR
and the counter substrate CT are pasted together by seal material
SB outside of the display area R1, in which the predetermined cell
gap is formed.
[0059] The liquid crystal layer LQ is held at the cell gap formed
between the array substrate AR and the counter substrate CT, and is
arranged between the first alignment film AL1 and the second
alignment film AL2. The liquid crystal layer LQ contains the liquid
crystal molecule which is constituted by positive type liquid
crystal material. In addition, the gap Ga between the main pixel
electrode PAB and the main common electrode CA is larger than the
thickness of the liquid crystal layer LQ, and practically, it is
desirable that the gap Ga has a thickness larger than twice that of
the liquid crystal layer LQ. Regarding the relation among the
thickness of the liquid crystal layer LQ, the gap Ga and the gap
Gb, the gap Ga is larger than that of the liquid crystal layer LQ,
and smaller than the gap Gb. That is, it is desirable to have a
following relation: the thickness of the liquid crystal layer
LQ<Ga<Gb.
[0060] A first optical element OD1 is attached on an external
surface 10B of the array substrate AR, i.e., the external surface
of the first insulating substrate 10 which constitutes the array
substrate AR, by adhesives, etc. The first optical element OD1 is
located on a side which counters with the backlight unit 4 of the
liquid crystal display panel LPN, and controls the polarization
state of the incident light which enters into the liquid crystal
display panel LPN from the backlight unit 4. The first optical
element OD1 includes a first polarizing plate PL1 having a first
polarization axis (or first absorption axis) AX1.
[0061] A second optical element OD2 is attached on an external
surface 20B of the counter substrate CT, i.e., the external surface
of the second insulating substrate 20 which constitutes the counter
substrate CT, by adhesives, etc. The second optical element OD2 is
located on a display surface side of the liquid crystal display
panel LPN, and controls the polarization state of emitted light
from the liquid crystal display panel LPN. The second optical
element OD2 includes a second polarizing plate PL2 having a second
polarization axis (or second absorption axis) AX2.
[0062] The first polarization axis AX1 of the first polarizing
plate PL1 and the second polarization axis AX2 of the second
polarizing plate PL2 are arranged in the Cross Nicol state in which
they substantially intersects perpendicularly. At this time, one
polarizing plate is arranged, for example, so that its polarization
axis is arranged in the initial aliment direction, that is, in
parallel with or in orthogonal with the first alignment treatment
direction PD1 or the second alignment treatment direction PD2. When
the initial alignment direction is in parallel with the second
direction Y, the polarizing axes of one polarizing plate is in
parallel with the second direction Y or the first direction X.
[0063] An example shown in FIG. 2B, the first polarizing plate PL1
is arranged, for example, so that the first polarization axis AX1
is arranged orthogonally crossing the initial alignment direction
(second direction Y) of the liquid crystal molecule LM, i.e., in
parallel with the first direction X. The second polarizing plate
PL2 is arranged, for example, so that the second polarization axis
AX2 is arranged in parallel with the initial alignment direction
(second direction Y) of the liquid crystal molecule LM.
[0064] An example shown in FIG. 2C, the second polarizing plate PL2
is arranged, for example, so that the second polarization axis AX2
is arranged orthogonally crossing the initial alignment direction
(second direction Y) of the liquid crystal molecule LM, i.e., in
parallel with the first direction X. The first polarizing plate PL1
is arranged, for example, so that the first polarization axis AX1
is arranged in parallel with the initial alignment direction
(second direction Y) of the liquid crystal molecule LM.
[0065] Next, the operation of the liquid crystal display panel LPN
of the above-mentioned structure is explained. As shown in FIGS. 2A
and 2B, and FIG. 3, at the time of non-electric field state (OFF),
i.e., when a potential difference (i.e., electric field) is not
formed between the pixel electrode PE and the common electrode CE,
the liquid crystal molecules LM of the liquid crystal layer LQ are
aligned so that their long axis are aligned in parallel with the
first alignment treatment direction PD1 of the first alignment film
AL1 and the second alignment treatment direction PD2 of the second
alignment film AL2 as shown with a dashed line in the figure. In
this state, the time of OFF corresponds to the initial alignment
state, and the alignment direction of the liquid crystal molecule
LM corresponds to the initial alignment direction.
[0066] In addition, precisely, the liquid crystal molecules LM are
not exclusively aligned in parallel with the X-Y plane, but are
pre-tilted in many cases. For this reason, the precise direction of
the initial alignment is a direction in which an orthogonal
projection of the alignment direction of the liquid crystal
molecule LM at the time of OFF is carried out to the X-Y plane.
Hereinafter, the explanation is made in the presumption that the
liquid crystal molecules LM are aligned in parallel with the X-Y
plane and rotates in a plane in parallel with the X-Y plane to
simplify the explanation.
[0067] Here, both of the first alignment treatment direction PD1 of
the first alignment film AL1 and the second alignment treatment
direction PD2 of the second alignment film AL2 are directions in
parallel to the second direction Y each other. At the time of OFF,
the long axis of the liquid crystal molecule LM is initially
aligned substantially in parallel to the second direction Y as
shown with a dashed line in FIG. 2A. That is, the initial alignment
direction of the liquid crystal molecule LM is in parallel to the
second direction Y, i.e., makes an angle of 0.degree. with respect
to the second direction Y.
[0068] In the cross-section of the liquid crystal layer LQ, when
the first alignment direction PD1 and the second alignment
direction PD2 are in parallel and the same direction each other,
the liquid crystal molecule LM is aligned substantially in the
horizontal direction (pre-tilt angle is substantially zero) near
the intermediate portion of the liquid crystal layer LQ. The liquid
crystal molecule LM is aligned with a pre-tilt angle which becomes
symmetrical with respect to the intermediate portion in a portion
near the first alignment film AL1 and a portion near the second
alignment film AL2. That is, the liquid crystal molecule LM is
aligned in the splay alignment state.
[0069] Here, the liquid crystal molecule LM near the first
alignment film AL1 is initially aligned in the first alignment
treatment direction PD1 by performing the alignment processing in
the first alignment treatment direction PD1, and the liquid crystal
molecule LM near the second alignment film AL2 is initially aligned
in the second alignment treatment direction PD2 by performing the
alignment processing in the second alignment treatment direction
PD2. When the first alignment treatment direction PD1 and the
second alignment treatment direction PD2 are in parallel and the
same direction, the liquid crystal molecule LM becomes the splay
alignment state, that is, aligns substantially in the horizontal
direction near the intermediate portion of the liquid crystal layer
LQ. The liquid crystal molecule LM aligns in symmetrical with
respect to the intermediate portion in vicinities of the first
alignment film AL1 on the array substrate AR and the second
alignment film AL2 on the counter substrate CT. In the splay
alignment state of the liquid crystal molecule LM, the display is
optically compensated even in an inclining direction from the
normal direction of the substrate by the molecules near the first
alignment film AL1 and the second alignment film AL2. Therefore,
when the first alignment film AL1 and the second alignment film AL2
are in parallel and the same direction mutually, optical leak is
hardly generated in a black state. Accordingly, high contrast ratio
can be realized, and it becomes possible to improve display
grace.
[0070] In addition, when the first alignment treatment direction
PD1 and the second alignment treatment direction PD2 are in
parallel and opposite direction each other in the cross section of
the liquid crystal layer LQ, the liquid crystal molecule LM aligns
with a uniform pre-tilt angle in the intermediate portion, near the
first alignment film AL1, and near the second alignment film AL2 of
the liquid crystal layer LQ (homogeneous alignment).
[0071] The backlight from the backlight 4 penetrates the first
polarizing plate PL1, and enters into the liquid crystal display
panel LPN. The polarization state of the incident light changes
with the alignment state of the liquid crystal molecule LM when the
incident light passes the liquid crystal layer LQ. The incident
light which penetrates the liquid crystal display panel LPN is
absorbed by the second polarizing plate PL2 (black display).
[0072] On the other hand, in case potential difference (or electric
field) is formed between the pixel electrode PE and the common
electrode CE, i.e., at the time of ON, the lateral electric field
(or oblique electric field) is formed in parallel with the
substrates between the pixel electrode PE and the common electrode
CE. The liquid crystal molecules LM are affected by the electric
field between the pixel electrode PE and the common electrode CE,
and the long axis thereof rotates in parallel with the X-Y plane as
shown with a solid line in the figure.
[0073] In the example shown in FIG. 2A, in the region between the
pixel electrode PE and the main common electrode CAL, the liquid
crystal molecule LM mainly rotates clockwise to the second
direction Y, and aligns so that it may turn to the lower left in
the figure. On the other hand, in the region between the pixel
electrode PE and the main common electrode CAR, the liquid crystal
molecule LM mainly rotates counterclockwise to the second direction
Y, and aligns so that it may turn to the lower light in the
figure.
[0074] Thus, in each pixel PX, in case electric field is formed
between the pixel electrode PE and the common electrode CE, the
alignment direction of the liquid crystal molecule LM is divided
into two or more directions by the position which overlaps with the
pixel electrode PE, and domains are formed in each alignment
direction. That is, two or more domains are formed in one pixel
PX.
[0075] At the time ON as above, a portion of the backlight from the
backlight 4 penetrates the first polarizing plate PL1, and enters
into the liquid crystal display panel LPN. The polarization state
of the incident light changes with the alignment state of the
liquid crystal molecule LM when the incident light passes the
liquid crystal layer LQ. At the time ON, a portion of the incident
light which penetrates the liquid crystal display panel LPN passes
the second polarizing plate PL2 (white display).
[0076] FIG. 4 is a figure showing an electric field formed between
the pixel electrode PE and the common electrode CE in the liquid
crystal display panel LPN shown in FIG. 2, and a relation between a
director and a transmissivity of the liquid crystal molecule by
this electric field.
[0077] As shown in FIG. 4, in the OFF state, the liquid crystal
molecule LM is initially aligned substantially in parallel with the
second direction Y. In the ON state in which potential difference
is formed between the pixel electrode PE and the common electrode
CE, when the director or the long axes direction of the liquid
crystal molecule LM is shifted substantially by 45.degree. in the
X-Y plane with respect to the first polarization axis AX1 of the
first polarizing plate PL1 and the second polarization axis AX2 of
the second polarizing plate PL2, an optical modulation rate of the
liquid crystal molecule becomes the highest. That is, the
transmissivity in the aperture portion becomes the maximum.
[0078] In the illustrated example, when the liquid crystal molecule
changes into the ON state, the director of the liquid crystal
molecule LM between the main common electrode CAL and the pixel
electrode PE becomes substantially in parallel with a direction of
45.degree.-225.degree. in the X-Y plane. The director of the liquid
crystal molecule LM between the main common electrode CAR and the
pixel electrode PE becomes substantially in parallel with a
direction of 135.degree.-315.degree. in the X-Y plane, and a peak
transmissivity is obtained. At this time, if the transmissivity
distribution per one pixel is focused, while the transmissivity
becomes substantially zero on the pixel electrode PE and the common
electrode CE, high transmissivity is obtained in the whole
electrode gap between the pixel electrode PE and the common
electrode CE.
[0079] Here, the inventors investigated the display properties of
the liquid crystal display device according to this embodiment. In
addition, the display properties of the liquid crystal display
device according to a comparative example of this embodiment were
investigated.
[0080] The structure of the liquid crystal display device according
to the comparative example is explained. FIG. 5 is a plan view
schematically showing a structure of one pixel when the liquid
crystal display panel of the comparative example of the embodiment
is seen from the counter substrate side
[0081] As shown in FIG. 5, each pixel PX has two regions R3 in
which the inter-electrode distance Ga between the main pixel
electrode PAB and the main common electrode CA and between the main
pixel electrode PAU and the main common electrode CA in the first
direction X is substantially the same. In this comparative example,
the widths of the main pixel electrode PAB and the main pixel
electrode PAU are the same. In addition, other structures are
formed like the liquid crystal display device according to this
embodiment.
[0082] FIG. 6 is a figure showing the change of transmissivity T
with respect to voltage (potential difference between the pixel
electrode PE and the common electrode CE) in the liquid crystal
display devices according to the embodiment and the comparative
example in a graph.
[0083] Since the inter electrode distance is formed so as to be
Ga<Gb as shown in FIG. 2A, if the voltage V (potential
difference between the pixel electrode PE and the common electrode
CE) becomes high as shown in FIG. 6, it turns out that firstly, the
rise of the transmissivity T starts in the region R3, and then the
rise of the transmissivity T starts in the region R4 when the
voltage V becomes higher. The transmissivity T becomes almost the
same in the regions R3 and R4 and the maximum if the voltage V
becomes much higher. For this reason, it turns out that the same
effect as that by a half-tone driving is acquired only by adjusting
the voltage V.
[0084] FIG. 7 is a figure showing the change of relative brightness
L* with respect to gradient at the time of white display in the
liquid crystal display devices according to the embodiment and the
comparative example in a graph. As shown in FIG. 7, it turns out
that the brightness in the front direction (0 deg) of the liquid
crystal display device according to this embodiment and the
comparative example is the same, each other.
[0085] On the other hand, it turns out that the brightness of the
liquid crystal display device in an oblique direction (50 deg)
inclining by 50.degree. from the front direction to the horizontal
direction (first direction X) according to this embodiment and the
comparative example is higher than the brightness in the front
direction at most of the gradients. This is because the generation
of the light leak in the black state is resulted in the oblique
direction.
[0086] However, when comparing the brightness of the liquid crystal
display device according to this embodiment with the liquid crystal
display device of the comparative example in the oblique direction
is measured, it turns out that the brightness of the liquid crystal
display device according to this embodiment is closer to the
brightness in the front direction than the brightness of the liquid
crystal display device of the comparative example. Especially, in a
gray level, it turns out that the brightness of the liquid crystal
display device in the oblique direction according to this
embodiment is close to the brightness in the front direction.
[0087] The pixel PX of the liquid crystal display device according
to the comparative example shows only the V-T characteristic of the
region R3 in FIG. 6. On the other hand, the pixel PX of the liquid
crystal display device according to this embodiment shows both of
the V-T characteristics of the regions R3 and R4 in FIG. 6. Since
the light leak in the black state in the oblique direction can be
controlled, the liquid crystal display device can contribute to
expansion of a viewing angle.
[0088] In the liquid crystal display device according to this
embodiment as mentioned above, the liquid crystal display device is
equipped with the array substrate AR, the counter substrate CT, the
liquid crystal layer LQ, and the plurality of pixels PX. The pixel
PX includes the main pixel electrode PA formed on the array
substrate AR extending along the second direction Y, and the main
common electrodes CA formed on the counter substrate CT extending
along the second direction Y so as to sandwich the main pixel
electrode PA therebetween in the first direction X.
[0089] Each pixel PX includes two regions R3 and R4 in which the
inter-electrode distance between the main pixel electrode PA and
the main common electrode CA in the first direction X differs
mutually. In the above embodiment, the width of the main pixel
electrode PA in the first direction X is changed in the region R3
and the region R4. Since the generating of the light leak in the
black state in the oblique direction can be controlled, the
embodiment can contribute to the expansion of the viewing
angle.
[0090] Moreover, according to this embodiment, since it becomes
possible to obtain high transmissivity in the electrode gap between
the pixel electrode PE and the common electrode CE, it becomes
possible to correspond by expanding the inter-electrode distance
between the pixel electrode PE and the main common electrode CA in
order to make transmissivity of each pixel high enough. Further, in
the product specifications in which a pixel pitch differs each
other, a transmissive distribution peak shown in FIG. 4 can be used
by changing the inter-electrode distance, i.e., by changing the
width of the pixel electrode PE arranged substantially in the
center of the pixel PX. That is, in the display mode according to
this embodiment, it becomes possible to offer the display panel
having various pixel pitches by setting up the inter-electrode
distance without necessarily using microscopic processing
corresponding to the product specification from low resolution with
a comparatively large pixel pitch to high resolution with a
comparatively small pixel pitch. Therefore, it becomes possible to
realize the demand for high transmissivity and high resolution
easily.
[0091] Moreover, according to this embodiment, the transmissivity
fully falls in a region which overlaps with the black matrix BM.
This is because the leak of electric field does not occur outside
of the pixel from the common electrode CE, and undesired lateral
electric field is not produced between the adjoining pixels
sandwiching the black matrix BM. That is, it is because the liquid
crystal molecule which overlaps with the black matrix BM maintains
the initial alignment state like at the time OFF (or the time of
the black display). Accordingly, even if it is a case where the
colors of the color filter differ between the adjoining pixels, it
becomes possible to control the generating of mixed colors, and
also becomes possible to control the fall of color reproducibility
and the contrast ratio.
[0092] Moreover, when an assembling shift occurs between the array
substrate AR and the counter substrate CT, a difference may arise
in distances between the respective common electrodes CE of the
both sides of the pixel and the pixel electrode PE. However, since
the assembling shift is generated in common to all the pixels PX,
there is no difference in the electric field distribution between
the pixels PX, and the influence to the display of the image is
very small. Even if the assembling shift arises between the array
substrate AR and the counter substrate CT, it becomes possible to
control the undesirable electric field leak to the adjoining
pixels. For this reason, even if it is in a case where the colors
of the color filter differ between the adjoining pixels, it becomes
possible to control the generation of the mixed colors, and also
becomes possible to suppress the falls of color reproducibility
nature and the contrast ratio.
[0093] According to this embodiment, the main common electrodes CA
counter with the source lines S, respectively. When the main common
electrode CAL and the main common electrode CAR are especially
arranged on the source line S1 and the source line S2,
respectively, the aperture portion AP which contributes to the
display can be expanded as compared with the case where the main
common electrode CAL and the main common electrode CAR are arranged
on the pixel electrode PE side rather than above the source line S1
and the source line S2, and it becomes possible to improve the
transmissivity of the pixel PX.
[0094] Moreover, it becomes possible to expand the distances
between the pixel electrode PE and the main common electrode CAL,
and between the pixel electrode PE and the main common electrode
CAR by arranging each of the main common electrode CAL and the main
common electrode CAR above the source line S1 and the source line
S2, respectively, and also becomes possible to form the lateral
electric field closer to the horizontal direction. Therefore, it
becomes possible to maintain the feature of the wide view angle
which is a merit of the IPS mode.
[0095] Moreover, according to this embodiment, it becomes possible
to form two or more domains in one pixel. For this reason, the
viewing angle can be optically compensated in two or more
directions, and the wide viewing angle characteristics is
attained.
[0096] In addition, in the above-mentioned example, since the
liquid crystal layer LQ has positive dielectric constant
anisotropy, the case where the alignment direction of the liquid
crystal molecule LM is in parallel to the second direction Y is
explained. However, the initial alignment direction of the liquid
crystal molecule LM may be the oblique direction D which obliquely
crosses the second direction Y as shown in FIG. 2A. Herein, the
angle .theta.1 which the initial alignment direction D makes with
the second direction Y is larger 0.degree. and smaller than
45.degree.. In addition, it is extremely effective to set the angle
.theta.1 in the range of 5.degree. to 30.degree., more desirably
less than 20.degree. in a viewpoint of the alignment control of the
liquid crystal molecule LM. That is, it is desirable that the
initial alignment direction of the liquid crystal molecule LM is
set to a direction substantially in parallel with the direction in
the range of 0.degree. to 20.degree. with respect to the second
direction Y.
[0097] That is, it is desirable to form the first alignment film
AL1 so that the first alignment film AL1 initially aligns the
liquid crystal molecule LM in the vicinity of the alignment film in
the second direction Y or the oblique direction inclining from the
second direction Y within 20.degree.. It is also desirable to form
the second alignment film AL2 so that the second alignment film AL2
initially aligns the liquid crystal molecule LM in the vicinity of
the alignment film in the second direction Y or the oblique
direction inclining from the second direction Y within
20.degree..
[0098] Moreover, although the above-mentioned example explains the
case where the liquid crystal layer LQ has positive dielectric
constant anisotropy, the liquid crystal layer LQ may have negative
dielectric constant anisotropy. That is, n type liquid crystal
material may be used. Although detailed explanation is omitted,
when the negative type liquid crystal material is used, it is
desirable that the above-mentioned angle 6 1 is made in the range
of 45.degree. to 90.degree., and desirably not less than 70.degree.
because the dielectric constant anisotropy becomes a contrast
relation between the positive type and the negative type.
[0099] That is, it is desirable to form the first alignment film
AL1 so that the first alignment film AL1 initially aligns the
liquid crystal molecule LM in the vicinity of the alignment film in
the first direction X or the oblique direction inclining from the
first direction X within 20.degree.. It is also desirable to form
the second alignment film AL2 so that the second alignment film AL2
initially aligns the liquid crystal molecule LM in the vicinity of
the alignment film in the first direction X or the oblique
direction inclining from the first direction X within
20.degree..
[0100] Furthermore, even at the time of ON, since the lateral
electric field is hardly formed (or sufficient electric field to
drive the liquid crystal molecule LM is not formed) on the pixel
electrode PE or the common electrode CE, the liquid crystal
molecule LM hardly moves from the initial alignment direction like
at the time of OFF. For this reason, as mentioned-above, even if
the pixel electrode PE and the common electrode CE are formed of
the electric conductive material with the light transmissive
characteristics in these domains, the backlight hardly penetrates,
and hardly contributes to the display at the time of ON. Therefore,
the pixel electrode PE and the common electrode CE do not
necessarily need to be formed of a transparent electric conductive
material, and may be formed using non-transparent electric
conductive materials, such as aluminum (Al), silver (Ag), and
copper (Cu).
[0101] Furthermore, the common electrode CE may include a second
main common electrode (shield electrode) formed on the array
substrate AR facing the common electrode CA (or source line S) in
addition to the main common electrode CA formed on the counter
substrate CT. The second main common electrode extends
substantially in parallel with the main common electrode CA and is
set to the same potential as the main common electrode CA. It
becomes possible to shield undesirable electric field from the
source line S by providing the second common electrode.
[0102] Moreover, the common electrode CE may include a second
sub-common electrode (shield electrode) formed on the array
substrate AR facing the gate line G or the auxiliary capacitance
line C in addition to the main common electrode CA formed on the
counter substrate CT. The second sub-common electrode extends in a
direction crossing the main common electrode CA and set to the same
potential as the main common electrode CA. It becomes possible to
shield undesirable electric field from the gate line G or the
auxiliary capacitance line C by providing the second sub-common
electrode. It becomes possible further to control the decrease of
the display quality according to the structure in which the second
main common electrode and the second sub-common electrode are
provided. Thereby, a liquid crystal display device with the wide
viewing angle can be obtained.
[0103] The width of the main common electrode CA may be different
every region of each pixel. Since each pixel PX is required to have
several regions in which the inter-electrode distance between the
main pixel electrode PA and the main common electrode CA in the
first direction X differs mutually, it is possible to make the
width of at least either one of the main pixel electrode PA and the
main common electrode CA different in every region of each pixel
PX.
[0104] The number of the plurality of regions of the pixel PX, in
which the inter electrode distance between the main pixel electrode
PA and the main common electrode CA in the first direction X
differs mutually may not be limited to two, and may be three or
more.
[0105] FIG. 8 is a plan view schematically showing a structure of
one pixel when the liquid crystal display panel is seen from a
counter substrate CT side according to a second embodiment. As
shown in FIG. 8, the pixel electrode PE includes the main pixel
electrode PA, the sub-pixel electrode PF, and the sub-pixel
electrode PG electrically connected mutually. Hereinafter, in order
to distinguish the main pixel electrode PA, the main pixel
electrode on the upper side in the figure is called PAU, the main
pixel electrode on the lower left side in the figure is called
PALB, and the main pixel electrode on the lower right side in the
figure is called PARB.
[0106] The main pixel electrodes PALB and PARB linearly extend
along the second direction Y from the sub-pixel electrode PF to
near the lower end of the pixel PX. The main pixel electrodes PALB
and PARB are formed in the shape of a belt having substantially the
same width along the first direction X, respectively. The main
pixel electrode PAU linearly extends along the second direction Y
from the sub-pixel electrode PF to near the upper end of the pixel
PX. The main pixel electrode PAU is formed in the shape of a belt
having substantially the same width along the first direction X.
The sub-pixel electrodes PF and PG are formed more broadly than the
main pixel electrodes PALB, PARB, and PAU. The sub-pixel electrode
PF is arranged in the center of the pixel PX.
[0107] The common electrode CE includes a plurality of main common
electrodes CA and the sub-common electrode CB. Hereinafter, in
order to distinguish the main common electrodes CA, the main common
electrode arranged in a lower middle portion is called CACB.
[0108] The main common electrode CACB is formed on the counter
substrate CT side, and is formed integrally or continuously with
the sub-common electrode CB. The main common electrode CACB
linearly extends along the second direction Y from the sub-common
electrode CB to near the lower end of the pixel PX. The main common
electrode CACB is formed in the shape of a belt having
substantially the same width along the first direction X. In the
first direction X, the main common electrode CACB is arranged
between the main pixel electrode PALB and the main pixel electrode
PARB.
[0109] Each pixel PX includes two regions R3 and R4 in which the
inter-electrode distance between the main pixel electrode PA and
the main common electrode CA in the first direction X differs
mutually. In this embodiment, the inter-electrode distance between
the main pixel electrode PA and the main common electrode CA in the
first direction X differs in two regions R3 and R4 in each pixel
PX.
[0110] In the illustrated example, the main common electrode CA is
arranged in three lines along the first direction X in the region
R3, and is arranged in two lines along the first direction X in the
region R4. The inter-electrode distances between the main common
electrode CAL and the main pixel electrode PALB, the
inter-electrode distance between the main common electrode CACB and
the main pixel electrode PALB, the inter-electrode distance between
the main common electrode CACB and the main pixel electrode PARB,
and the inter-electrode distance between the main common electrode
CAR and the main pixel electrode PARB, respectively, in the first
direction X are substantially the same. The inter-electrode
distance between the main common electrode CAL and the main pixel
electrode PAU is substantially the same as that between the main
common electrode CAR and the main pixel electrode PAU in the X
direction.
[0111] The inter-electrode distance Ga between the main common
electrode CA and the main pixel electrode PA in the region R3 is
smaller than the inter-electrode distance Gb between the main
common electrode CA and the main pixel electrode PA in the region
R4. The region R3 and the region R4 are arranged in adjacent in the
second direction Y in each pixel PX.
[0112] In addition, the liquid crystal display device according to
the second embodiment is formed like the liquid crystal display
device according to the first embodiment. Each pixel PX of the
liquid crystal display device according to the second embodiment
includes the regions R3 and R4 in which the V-T characteristic
differs mutually like the pixel of the liquid crystal display
device according to the first embodiment. Also in the liquid
crystal display device according to the second embodiment, since
the light leak of in the black state in the oblique direction can
be controlled, the liquid crystal device can contribute to
expansion of the viewing angle.
[0113] In addition, the sub-pixel electrode PG in FIG. 2A and FIG.
8 may be eliminated.
[0114] Next, the comparative liquid crystal display device of the
second embodiment is explained. FIG. 9 is a plan view schematically
showing a structure of one pixel when the liquid crystal display
panel of the comparative example of the second embodiment shown in
FIG. 8 is seen from the counter substrate side.
[0115] As shown in FIG. 9, the pixel electrode PE includes the main
pixel electrode PA, the sub-pixel electrode PF, and the sub-pixel
electrode PG electrically connected mutually. Hereinafter, in order
to distinguish the main pixel electrode PA, the main pixel
electrode on the upper left side in the figure is called PALU, and
the main pixel electrode on the upper right side in the figure is
called PARU.
[0116] The main pixel electrodes PALU and PARU linearly extend
along the second direction Y from the sub-pixel electrode PF to
near the upper end of the pixel PX. The main pixel electrodes PALU
and PARU are formed in the shape of a belt having substantially the
same width along the first direction X, respectively. The sub-pixel
electrodes PF and PG are formed more broadly than the main pixel
electrodes PALU and PARU. The sub-pixel electrode PF is arranged in
the center of the pixel.
[0117] The common electrode CE includes a plurality of main common
electrodes CA and the sub-common electrode CB. Hereinafter, in
order to distinguish the main common electrodes CA, the main common
electrode arranged in an upper middle portion is called CACU.
[0118] The main common electrode CACU is formed on the counter
substrate CT side, and is formed integrally or continuously with
the sub-common electrode CB. The main common electrode CACU
linearly extends along the second direction Y from the sub-common
electrode CB to near the upper end of the pixel PX. The main common
electrode CACU is formed in the shape of a belt having
substantially the same width along the first direction X. In the
first direction X, the main common electrode CACU is located
between the main pixel electrode PALU and the main pixel electrode
PARU.
[0119] Each pixel PX includes two regions R3 in which the
inter-electrode distance between the main pixel electrode PA and
the main common electrode CA in the first direction X is the
same.
[0120] In the illustrated comparative example, the main common
electrode CA is arranged in three lines along the first direction X
in the two regions R3, respectively. The liquid crystal display
device of the above-mentioned comparative example is formed like
the liquid crystal display device according to the second
embodiment except above points. Since, in each pixel PX of the
liquid crystal display device of the above-mentioned comparative
example, only the regions R3 are provided, the pixel PX cannot
control the generating of the light leak in the black state in the
oblique direction as shown in FIG. 6 and FIG. 7
[0121] In the embodiments, the wiring layer which separates between
the region R3 and the region R4 of each pixel PX is not limited to
the auxiliary capacitance line C and the sub-common electrode CB,
and can be modified variously. That is, any wiring layers can be
used to separate the regions if the wirings are formed on the array
substrate AR or the counter substrate CT, and extend along the
first direction X. In each pixel PX, several regions in which the
inter-electrode distance between the main pixel electrode PA and
the main common electrode CA in the first direction X differ
mutually may be adjacent in the first direction X. That is, what is
necessary is that the regions are adjacent at least in either one
of the first direction X and the second direction X.
[0122] While certain embodiments have been described, these
embodiments have been presented by way of example only, and are not
intended to limit the scope of the inventions. Indeed, the novel
embodiments described herein may be embodied in a variety of other
forms; furthermore, various omissions, substitutions and changes in
the form of the embodiments described herein may be made without
departing from the spirit of the inventions. The accompanying
claims and their equivalents are intended to cover such forms or
modifications as would fall within the scope and spirit of the
inventions.
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